Example embodiments of inventive concepts relates to a method for extracting valuable elements from minerals, and more particularly, to a method for extracting rare earth elements from monazite included in the sea sand.
The rare earth element is a generic term of seventeen chemical elements including fifteen lanthanides whose atomic numbers are from 57 through 71 plus scandium and yttrium of the third group in the periodic table. There exist scare rare earth elements in the natural world, but demands for the rare earth elements as materials in high-tech industries such as electric, electronic, catalyst, optics, special metals, super conductors, and fluorescent substance has been rapidly increasing.
Meanwhile, the world concentrates on securing rare earth elements because not only producers such as China restricts exports strategically, but also the price of rare earth elements has been rising along with the recent price increase of raw materials.
Recently, methods for extracting rare earth elements from sea sand, especially, from monazite and bastnasite, has been tried to secure rare earth elements.
Monazite (RePO4, Re denotes rare earth elements) is a phosphate mineral in which rare earth elements and phosphates are combined, and main rare earth elements are cerium (Ce), lanthanum (La), and neodymium (Nd) with a small amount of praseodymium (Pr), gadolinium (Gd), and samarium (Sm). Also, uranium (U) and thorium (Th) may be obtained in the process of extracting from monazite or processing monazite as byproducts.
Economical methods among methods for extracting rare earth elements from monazite are acid leaching extracting rare earth elements by soaking monazite in sulfuric acid or hydrochloric acid, alkaline leaching extracting rare earth elements by soaking monazite in sodium hydroxide, and sintering in a high temperature along with sodium hydroxide or sodium phosphate.
However, such the methods have problems that elaborate adjustment for high temperature, pressure, and pH is required and it is not easy to extract rare earth elements. Especially, extracting rare earth elements at a high temperature, continuous producing of chemicals to adjust pH, and post-cleaning of the used chemicals expose problems.